1. Technical Field
The present invention relates to a radiator which conducts heat of an electronic component, a heat sink fan, and a radiator manufacturing method. Particularly, the present invention relates to a radiator which cools a cooling object such as an electronic component including an MPU, etc. The present application is relevant to the below-identified Japanese patent applications. The present application claims priorities from Japanese Patent Applications                1. Japanese Patent Application No. 2007-005490 filed on Jan. 15, 2007; and        2. Japanese Patent Application No. 2007-083091 filed on Mar. 27, 2007, the contents of which are incorporated herein by reference.        
2. Description of the Related Art
Recently, the clocking frequency of MPUs (Micro Processing Unit) has significantly increased, and heat generated by MPUs is increasing along with the increase of the clocking frequency. MPUs are subject to the risk of malfunctioning due to this heat generated by themselves, and cooling of MPUs is therefore a critical issue. Electronic components such as MPUs that generate heat are equipped with a heat sink fan in which a heat sink of a metal material formed of a plurality of radiating fins and a cooling fan which supplies cooling air to the heat sink are integrated. It is demanded that the cooling efficiency of the heat sink fan and the heat conductance from the MPU to the heat sink be improved.
On the other hand, there is a cost-cut demand for electronic devices including an MPU, most typically, personal computers. Accordingly, a heat sink that has a high cooling performance and at the same time can be manufactured at a low cost is demanded.
In order to improve the cooling efficiency of a heat sink, it is common to increase the surface area of the entire heat sink. The surface area can be increased by decreasing the circumference-wise thickness of the radiating fins, and assembling each radiating fin so as to radially extend outward in the diameter-wise direction. However, since the heat sink loses a bit of its robustness when the radiating fins become thinner, the extend to which the radiating fins can be thinned is limited. Furthermore, if there is left a too narrow space between the radiating fins at their starting end on a base, from which the radiating fins extend, the cooling air supplied to the heat sink does not smoothly flow between the radiating fins. Hence, it is not possible to improve the cooling efficiency simply by increasing the surface area of the heat sink.
In order to improve the cooling performance of a heat sink, it is necessary to form the heat sink such that conductance loss that might occur while heat is conducted from the MPU as the heat generator to the radiating fins becomes small. For example, Unexamined Japanese Patent Application Publication No. 2005-327854 discloses a heat sink comprising a base which is formed of a cylindrical hollow portion having a hollow thereinside, and a high heat conductance member snugly put inside the hollow portion so as to be capable of conducting heat to the hollow portion. Radiating fins are formed on the outer circumference of this base, and the high heat conductance member is made of copper that is higher in heat conductance than the material of the radiating fins and hollow portion (aluminum).
Further, to impart a high cooling performance to a heat sink, it is preferable to make the contact pressure at the contact interface between the heat sink and the MPU high. This is because if the contact pressure is high, it is possible to make the contact heat resistance, which is to occur between the heat sink and the MPU, small. In this case, it is necessary to appropriately fix the heat sink on the MPU to make the contact pressure between the heat sink and the MPU high.
Unexamined Japanese Patent Application Publication No. 2006-32941, for example, discloses a method of forming a groove in the outer circumferential surface of a core portion of a base, and fixing a support member (attaching member) to the heat sink such that an opening formed in the support member fits the groove. In addition to the method disclosed in Unexamined Japanese Patent Application Publication No. 2006-32941, there is known a method of sandwiching an attaching member between a heat sink and a core portion and fix them in this state.